1. Field of the Invention
The present invention relates to an RFID interrogator device that performs backscatter radio communication with RFID tags by using absorption and reflection of radio waves.
2. Description of the Related Art
Any RFID tag transmits, at a predetermined bit rate, a signal composed of a sync part, a response data part and an error detecting part. The sync part contains preamble data. U.S. Pat. No. 6,501,807 discloses an RFID interrogator device which compares preamble data preset in the device, with the preamble data of a signal the device has received and which determines that the signal received is a signal from an RFID tag if the preamble data of the signal is identical to the preset preamble data.
In the conventional RFID interrogator device, the preset preamble data is compared with the preamble data of any signal received. The signal the device has received inevitably contains noise. A part of the noise may be identical to the preset preamble data. In this case, the signal received will be mistaken for a signal from an RFID tag.